Here is a pic of my finder install:
I didn't want to drill any additional holes in the yak to run the wires through so I bought and extra screw in shock cord plug, drilled out the small hole to 5/8" so the transducer and power plugs would pass through. Still had a bit of space around the wiring so I installed a 3/8 I.D. rubber grommet as well. A tiny bit of goop to hold the grommet and just screw it in! Someone has probably already done this so I won't take credit for thinking of it but it made sense to me.
Fishfinder mounts to a Ram wedge mount and Ram Hummingbird specific mount.